I'm going to post Devon's request here. The best place to reply (for now) would be at the above link since it will give Devon an automatic notification.

Hi my name is Devon and I am a student at Peninsula College. I am currently a part of an undergraduate research project where we are attempting to build and IEC. At the moment we are trying to decide what level of vacuum pump we need for our fusor. I am looking through the books you offered in your blog but was hoping you could tell me how you came to a decision on a level of vacuum. Our advisor would like for us to prove mathematically what level we need.Thanks for your help,Devon

I tried to reply to this some where, but I can't find it now. Basicly I pointed out that you need to compute the density of particles from air and the density you need for fusion reactions. If you keep the ratio of the components of air constant (not how pumps really work, but close enough for a homework problem) then you can get the number density of particles you can live with.

The number density of particles you can live with is dependent on Paschen discharge.

Dr. B. says the maximum is 1E-6 torr.

You want the density to be as high as possible in order to maximize fusion.

Turbo pumps are rated in l/s pumping speed which for practical purposes in the region of interest is constant and independent of pressure.

So what you want to figure also is the input flow rate required to keep the pressure constant.

There is also the compression ratio problem. Turbo pumps have a compression ratio for H2 on the order of 1,000. So you need two pumps in series to get the outlet pressure up into the backing pump range (1 torr).

Derek Madison, one of the students involved in the Peninsula College Fusor Project reported to me in a voice mail that they achieved fusion on Jun 21. He says they will attempt to duplicate the results today Jun 23 at 10:30 AM in the Peninsula Physics lab.

Here are the Peninsula College students who made fusion on Jun 21, and again today on Jun 23. They detected their neutrons with a bubble detector purchased from Dr Derrico of Yale Univ (Yale will only sell their bubble detectors to other educational institutions.) Today I saw at least three bubbles appear in the gel in the little vial, after an exposure of about 1 minute at a distance of about 0.1 m from the chamber wall. Left to right: Devon (who originally contacted MSimon), Ivan, Sarah, Chris, Aaron, and Derek. They can be contacted through their advisor, Jeff Zirul: jeffz at pcadmin dot ctc dot edu.
Here is the vacuum chamber.
And here is the discharge glow.
I did my best to resolve the bubbles in the gel - but bad lighting and limited resolution got the best of me.
Bill Flint